The heli and the hoop

A helicopter with a large hoop dangling below it crisscrossed the north-eastern area of Ermelo on Thursday and Friday last week, causing much speculation as to what it was all about.

The Highvelder paid a visit to the Ermelo airfield to investigate and found that the helicopter had been commissioned by the South African National Roads Agency (SOC) Limited (Sanral) and was using high-tech airborne surveying equipment in order to plot possible routes for the construction of the proposed ring road.

The large hoop that hung below the helicopter was fitted with high-tech seismic equipment that emits impulses that are able to determine the depth and extent of underground cavities.

Sanral is investigating the construction of a ring road round the town that will divert through traffic from coming into town, while also conveniently inter-connecting with the three national roads, the N2, N11 and N17.

Three possible alternative routes for the ring road have been identified, and upgrading of the existing roads through Ermelo was investigated as a fourth alternative.  The ring road has been proposed in order to alleviate heavy vehicle traffic-flow on the main routes through the town.

A final decision will only be made based, among others, on the results of an independent Environmental Impact Assessment (EIA).

In the area north-east of Ermelo, old, abandoned underground coal mines exist, and available information is too unreliable to pronounce on the safety of this area to build a road across it.

To determine the location, depth and extent of these cavities by means of conventional borehole drilling would be very expensive, time-consuming and highly intrusive on the ground above, and possibly still not be reliable enough.

Sanral has therefore begun with a highly advanced geo-physical survey to determine the location, depth and extent of these underground cavities so as to determine the safety of route alternatives. The survey is to be followed up with more detailed ground-geophysical investigations and possibly even limited borehole drilling.  This process may take up to three months to conclude, excluding the December holiday period.

Mr Klaus Schmid, Sanral’s project engineer who is managing the Ermelo ring road, said the three-pronged geophysical survey of the area should provide adequately detailed information to enable determination of a preferred route.

“As far as we are aware, this three-phased geophysical survey is the first application of advanced mining exploration technology for road purposes in Africa. The equipment can scan at least up to 60m below surface, which is the target depth of the first phase investigation,” Schmid explained.

He further explained that the data obtained from the airborne survey will be further processed and analysed by geo-physical specialists. All stakeholders affected by this project will be informed of key developments.

Schmid said all this work will provide more detailed and accurate information regarding the stability and safety of the ground for the alternative routes.

“This will help Sanral to make an informed decision about the safest and most appropriate route to use when constructing the ring road,” he said.

Schmid said the EIA process must still run its course, with further public participation planned for 2015 as soon as the route choice has been made.